Theory of nonionic hydrophobic solutes in mixture solvent: Solvent-mediated interaction and solute-induced phase separation

Abstract

We present a theory of nonionic solutes in a mixture solvent composed of water-like and alcohol-like species. First, we show relationship among the solvation chemical potential, the partial volumes $v_i$, the Kirkwood-Buff integrals, the second osmotic virial coefficient, and the Gibbs transfer free energy. We examine how the solute density $n_3$ is coupled to the solvent densities $n_1$ and $n_2$ in thermodynamics. In the limit of small compressibility, we show that the space-filling condition ${\sum }_i{v}_i{n}_i=1$ nearly holds for inhomogeneous densities $n_i$, where the concentration fluctuations of the solvent can give rise to a large solute-solute attractive interaction. We also derive a solute spinodal density $n_3^{\mathrm{spi}}$ for solute-induced instability. Next, we examine gas-liquid and liquid-liquid phase transitions induced by a small amount of a solute using the Mansoori, Carnahan, Starling, and Leland model for hard-sphere mixtures $[${ J. Chem. Phys.} {\bf 54}, 1523 (1971)$]$. Here, we assume that the solvent is close to its gas-liquid coexistence and the solute interacts repulsively with the water-like species but attractively with the alcohol-like one. We calculate the binodal and spinodal curves in the phase diagrams and examine nucleation for these two phase transitions.

arXiv comment19 pages, 14 figures, accepted for publication in J. Chem. Phys

References in corpus (5)

• Methanol-water solutions: a bi-percolating liquid mixture
• Precipitation in aqueous mixtures with addition of strongly hydrophilic or hydrophobic solute
• Structure Formation due to Antagonistic Salts
• Electric double layer composed of an antagonistic salt in an aqueous mixture: Local charge separation and surface phase transition
• Density functional theory of gas-liquid phase separation in dilute binary mixtures

Cited by in corpus (4)

• Theory of electrolytes including steric, attractive, and hydration interactions
• Core-softened water-alcohol mixtures: the solute-size effects
• How antagonistic salts cause nematic ordering and behave like diblock copolymers
• Fluctuating hydrodynamics of dilute electrolyte solutions: systematic perturbation calculation of effective transport coefficients governing large-scale dynamics